A variety of computing technology exists that time-stamps data within a data storage system. For example, most operating systems record the date and time that each file was most recently saved. Some operating systems also record the creation date and time for each file.
Revision control systems track changes to a file each time it is saved, and allow a user to select between the various save points when retrieving the file. This maintains the initial contents of the file and all changes made to the file each time it was saved, and allows the user to retrieve any version of the file that was previously saved.